1. Field of the Invention
The present invention generally relates to rotatable joints, and more particularly, to a mechanical double joint system.
2. Discussion of the Related Art
Rotatable joints accommodates movement for arms of mechanical devices. As such, a mechanical device, having an arm designed for movement, includes a rotatable joint. The rotatable joint may join an arm or an actuating portion to a supporting portion (generally the body) of the mechanical device. In other words, the actuating portion is attached to the supporting portion by the rotatable joint. A typical actuating portion includes a base fixed to the supporting portion, a movable member fixed to the actuating portion, and a pivot shaft for connecting the base and the movable member. A pivot hole is defined in the base, and an end of the pivot shaft is rotatably engaged in the pivot hole. The other end of the pivot shaft is rotatably connected to the movable member by a pin. Thus, the movable member not only can rotate together with the pivot shaft relative to the base, but can also rotate relative to the pivot shaft.
Due to frictional force, wear and tear of usage, the pivot shaft and the pin of the rotatable joint may become worn out, thus the rotatable joint may become unstable and control of the actuating portion may suffer.
Therefore, a mechanical double joint system that is less likely to be worn out, and to be stable over the long term, is desired.